For example, the pigmentation which are caused on the skin after the suntan or sunburn, the freckle, the chloasma, and the senile pigment freckle, reside in such a state that the melanin production is extremely facilitated or enhanced on account of the activation of the pigment cell (melanocyte) existing in the skin. The component, which is well-known to have the function for preventing or ameliorating the occurrence and the deterioration of the skin pigment trouble as described above, is the compound (skin whitening agent) having the skin whitening function including, for example, ascorbic acid and its derivatives, hydrogen peroxide, colloidal sulfur, glutathione, hydroquinone, and catechol (see, for example, Non-Patent Document 1 and Non-Patent Document 2). External preparations for skin, which are blended with the components as described above as the active ingredients, are widely used. At present, a variety of mechanisms of action, including, for example, the tyrosinase enzyme inhibiting action, the tyrosinase-related protein degradation, and the melanin transfer inhibition caused by the suppression of dendrite elongation in melanocyte have been reported as the mechanism of action exhibited by the compound known as the skin whitening agent. Target molecules are present with respect to the respective mechanisms of action. In order to appropriately exert the action on the target molecule and express the high skin whitening effect, an organic low molecular weight compound, which appropriately interacts with the target molecule, is useful. Further, the organic low molecular weight compound, which appropriately interacts with each of the target molecules, has the structural properties which differs depending on each of the target molecules. Therefore, studies are vigorously performed as well in relation to the optimization of the chemical structure in order to maximally make the use of the pharmacological action exhibited by the organic low molecular weight compound. Further, at present, studies on the skin whitening agent are not limited to the compound which has the high efficacy and the high selectivity with respect to the existing target molecule, and studies are widened, for example, to the compound which simultaneously acts on a plurality of skin whitening target molecules and the compound which has a novel mechanism of action. The excellent skin whitening function is expected for such skin whitening agent. Actually, the screening has been carried out in relation to compounds having excellent skin whitening functions to seek for useful compounds which have various chemical structures or pharmacological characteristics. Any skin whitening agent, which has a novel scaffold nucleus, is still demanded even now.
Amino acid is the general term of organic compounds having both functional groups of amino group and carboxyl group in each of molecules thereof. In particular, studies are vigorously made about α-amino acid as the constitutive unit of protein to express various functions in the living body. Various physiological activities have been reported for α-amino acids including, for example, cysteine, arginine, valine, threonine, serine, and glycine existing in the living body as well as peptide derivatives including α-amino acids as constitutive elements. Even in the case of only the field of the cosmetics, the biological activities, which are known to be possessed by α-amino acids and derivatives thereof, include the actions of, for example, the antiaging action (see, for example, Patent Document 1), the moistening action (see, for example, Patent Document 2), the skin whitening action (see, for example, Patent Document 3), and the surface activating action. α-Amino acids and derivatives thereof are blended, for example, in cosmetic preparations in order to obtain the effects thereof. In general, the amino acids and the derivatives thereof as described above are excellent in the solubility, especially in the water solubility in addition to the efficacy, and the high safety is expected as well. Therefore, the blending in the cosmetic or the like is vigorously studied. However, it is hardly affirmed that the biological activities of, for example, the antiaging action, the moistening action, or the skin whitening action, which are possessed by α-amino acids and derivatives thereof as described above, are sufficiently efficacious. Studies are continuously made in relation to α-amino acids and derivatives thereof in order to enhance the biological activity. According to a study in relation to a serine derivative of amino acids and derivatives thereof as described above, it is known that N-methylserine has the moistening action (see, for example, Patent Document 4), the rough skin ameliorating effect and the wrinkle decreasing effect (see, for example, Patent Document 5), and the action to enhance the melanin production suppressing action of glabridin (see, for example, Patent Document 6). Further, it is known that N-benzoylserine has the moistening action (see, for example, Patent Document 7) and the wrinkle preventing or ameliorating action (see, for example, Patent Document 8). However, any skin whitening effect has not been clarified in relation to the serine derivatives as described above. It has not been known at all that the compound represented by the general formula (1) described above, the isomer thereof, and/or the pharmacologically acceptable salt thereof has/have the prophylactic or ameliorating action for preventing or ameliorating the pigmentation.